Alternator woes: Failing Voltage Regulator? - Page 2 - PeachParts Mercedes-Benz Forum

my123ca · #16 02-01-2013, 01:08 PM

Quote:

Originally Posted by haromaster87

Also, I have one of the smaller stock Bosch alternators that I had bought just a couple months before I bought the AL129X unit. It's still sitting in my garage and has hardly any miles on it. After looking at these 2 units, it looks like they might use the same Voltage Regulator. Would anyone know anything about that?

Thanks!

-Tony

It could work. They have the same shape.

haromaster87 · #17 02-01-2013, 02:51 PM

Quote:

Originally Posted by funola

Is your AL129X new or used? Does it use the plug in connector or hard wired?

It was bought as new or remanufactured, can't remember. But it was from an Ebay place so no telling the quality of the regulator they put in.

Quote:

Originally Posted by my123ca

It could work. They have the same shape.

I suppose this is right, but I've already got the new one ordered and it was cheap enough.

funola · #18 02-01-2013, 03:21 PM

Quote:

Originally Posted by haromaster87

It was bought as new or remanufactured, can't remember. But it was from an Ebay place so no telling the quality of the regulator they put in.

Are the belts tight and tensioned correctly? Does not sound like a regulator since it is a new or rebuilt unit which should have a regulator with new brushes.

When you had the fluctuating voltages, were there any relay clicking sound? Could be a malfunctioning glow plug relay pulling the voltage down.

haromaster87 · #19 02-01-2013, 04:33 PM

Quote:

Originally Posted by funola

Are the belts tight and tensioned correctly? Does not sound like a regulator since it is a new or rebuilt unit which should have a regulator with new brushes.

When you had the fluctuating voltages, were there any relay clicking sound? Could be a malfunctioning glow plug relay pulling the voltage down.

I would have thought so too, but are there any other components in a voltage regulator that can fail besides the brushes?

And that is a good idea, but I did not hear any clicks. Although I'm not sure that I would've been able to hear the clicks over the engine. However, that wouldn't explain that at this time the issue of the fluctuating voltage has not happened and now the issue is the volt meter being at 14v non stop. As I said, it would go between 12.5v at idle and hit a high of 14v at certain engine speeds. I don't know a great deal about voltage regulators, but if one was failing, would it have issues regulating voltage?

Graplr · #20 02-01-2013, 04:44 PM

In my experience, a flickering glow plug relay turns on the dash glow plug light.

It does sound like a bad connection somewhere but you have stated that you checked and cleaned all the connections, so you likely can rule that out.

How did you determine that the volt gauge was working? If it were me, next I would check the voltage with a different meter when the gauge was flickering. You can get one to plug into your cigarette lighter cheap. where is your gauge connected? It could be a loose connection on the gauge that shows up at idle when the engine is shaking.

funola · #21 02-01-2013, 04:45 PM

Quote:

Originally Posted by haromaster87

I would have thought so too, but are there any other components in a voltage regulator that can fail besides the brushes?

And that is a good idea, but I did not hear any clicks. Although I'm not sure that I would've been able to hear the clicks over the engine. However, that wouldn't explain that at this time the issue of the fluctuating voltage has not happened and now the issue is the volt meter being at 14v non stop. As I said, it would go between 12.5v at idle and hit a high of 14v at certain engine speeds. I don't know a great deal about voltage regulators, but if one was failing, would it have issues regulating voltage?

There is a resistor and a solid state device in the regulator that can go bad. That seldom happens unless abused, such as revering polarity or exceeding it's rating in V and A overheating it.

14 V is normal charging voltage (13.4 to 14.4). 12.5 is not. Have you had the battery tested?

haromaster87 · #22 02-01-2013, 04:52 PM

Quote:

Originally Posted by funola

There is a resistor and a solid state device in the regulator that can go bad. That seldom happens unless abused, such as revering polarity or exceeding it's rating in V and A overheating it.

14 V is normal charging voltage (13.4 to 14.4). 12.5 is not. Have you had the battery tested?

Ah I see. I wonder if one of those failed.

And yeah the battery is brand new actually. I'll have it tested. But based on the performance of it, I suspect battery is fine. The alternator has a smaller pulley on it which was necessary to fit it. And I don't know that 12.5v was the exact voltage at idle. Was likely closer to 13v, it's just now consistently sitting higher than it did before. It used to charge a higher voltage as the engine speeds increased and would max at about 14v, but now it just hits 14v at idle and just stays.

funola · #23 02-01-2013, 05:10 PM

Quote:

Originally Posted by haromaster87

Ah I see. I wonder if one of those failed.

And yeah the battery is brand new actually. I'll have it tested. But based on the performance of it, I suspect battery is fine. The alternator has a smaller pulley on it which was necessary to fit it. And I don't know that 12.5v was the exact voltage at idle. Was likely closer to 13v, it's just now consistently sitting higher than it did before. It used to charge a higher voltage as the engine speeds increased and would max at about 14v, but now it just hits 14v at idle and just stays.

If your battery is new, and you had this issue: "Then at random it would go crazy and jump between what looks like about 11-15 volts, and it would jump back and forth and the lights would dim and brighten until I applied a bit of throttle, then it would smooth out."

The lights should not dim or brighten with a good fully charged battery and blipping the throttle should not do that. Sounds like a wiring problem- bad grounds for the lights maybe. Which lights was doing that? Cluster or headlights?

Silber Adler · #24 02-01-2013, 06:02 PM

I think you have it. The battery wouldn't jump up and down on voltage if the alternator or regulator was kicking in or out. The battery would decrease very gradually over seconds if the alternator was flickering. It would stay about 11.5-12.5 depending on the load on it. I doubt if the voltage would change fast.

Has the gauge been tested. A loose wire there can make it move very quickly. Have you verified the system voltage with another VOM?

It is interesting to see the variety of thoughtful answers that you get.

Quote:

Originally Posted by funola

If your battery is new, and you had this issue: "Then at random it would go crazy and jump between what looks like about 11-15 volts, and it would jump back and forth and the lights would dim and brighten until I applied a bit of throttle, then it would smooth out."

The lights should not dim or brighten with a good fully charged battery and blipping the throttle should not do that. Sounds like a wiring problem- bad grounds for the lights maybe. Which lights was doing that? Cluster or headlights?

haromaster87 · #25 02-01-2013, 06:03 PM

Quote:

Originally Posted by funola

If your battery is new, and you had this issue: "Then at random it would go crazy and jump between what looks like about 11-15 volts, and it would jump back and forth and the lights would dim and brighten until I applied a bit of throttle, then it would smooth out."

The lights should not dim or brighten with a good fully charged battery and blipping the throttle should not do that. Sounds like a wiring problem- bad grounds for the lights maybe. Which lights was doing that? Cluster or headlights?

It was the headlights. That is all a good point though. I mean, the light flicker was minimal, like the difference between the lights running of just battery or off alternator. As if the alternator was coming and going. I'm going to recheck all my cables again.